Is there a way to apply mod_security to specific directories?

I'm pretty new to apache configurations, so hopefully this is an easy fix.

I read the how-to on mod_security - very informative and very useful, but I need more specific help on this.

What I'm trying to do is set up a downloads folder so that registered users of one of my sites can click on a link and download a file. I need to secure said folder from people not linking from the site (as the link will only appear for registered users). Is there a way to set up the conf file to apply security settings to a specific directory rather than the entire webhost? Is there a better way to accomplish this? I believe the directive that I'm looking for is

Code:

SetFilter !php

Thanks in advance for the help, and let me know if you need more information.